gistfile1.txt

function getShortestUniqueSubstring(arr, str):
   t = 0
   result = null
   uniqueCounter = 0
   countMap = new Map()
   # initialize countMap:
   for i from 0 to length(arr)-1:
      countMap.setValueOf(arr[i], 0)
   # scan str
   for h from 0 to length(str)-1:
      # handle the new head
      head = str.charAt(h)
      if countMap.keyExists(head) == false:
         continue
      headCount = countMap.getValueOf(head)
      if headCount == 0:
         uniqueCounter = uniqueCounter + 1
      countMap.setValueOf(head, headCount + 1)   
      # push tail forward
      while uniqueCounter == length(arr):
         tempLength = h - t + 1
         if tempLength == arr.length:
            return str.substring(t, h)
         if (!result or tempLength < length(result)):
            result = str.substring(t, h)
         tail = str.charAt(t) 
         if countMap.keyExists(tail):
            tailCount = countMap.getValueOf(tail) - 1
            if tailCount == 0:
               uniqueCounter = uniqueCounter - 1
            countMap.setValueFor(tail, tailCount)
         t = t + 1
    return result


given arr of unique characters and string str, find the shortest
substring that contains all the characters from arr